JP3925977B2 - Transparent conductive film, method for producing the same, and sputtering target - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transparent conductive film, a method for producing the same, and a sputtering target.
[0002]
[Prior art]
The transparent conductive film has both high visible light transmittance and high conductivity, such as a liquid crystal display element, a transparent electrode of a display element such as a plasma light emitting element, a transparent electrode of a solar cell, a heat ray reflective film of glass for automobiles or buildings, a CRT. It is widely used as a transparent heating element for various types of anti-fogging, such as an antistatic film or a refrigerated showcase.
[0003]
Conventionally, ITO (tin-doped indium oxide) has been widely used as a display element electrode because a low resistance film can be easily obtained as a transparent conductive film. In addition, a low-cost zinc oxide-based transparent conductive film and a low-cost, highly chemical-resistant tin oxide-based transparent conductive film are also known.
[0004]
As a problem of the conventional transparent conductive film material, ITO is expensive because indium which is the main component thereof is expensive, which is an obstacle to cost reduction. Zinc oxide-based materials have low chemical resistance against acids and alkalis, making it difficult to apply to industrial products such as display elements of zinc oxide-based transparent conductive films.
[0005]
Tin oxide is produced by spraying or CVD as an industrial manufacturing method, but it is difficult to form a uniform film thickness, and waste liquids such as chlorine and hydrogen chloride generated during film formation are difficult. Or there was a problem of environmental pollution by exhaust gas. As described above, the tin oxide-based transparent conductive film is useful as described above, but has various problems.
Further, the crystalline tin oxide film has a problem of low scratch resistance. The reason why the scratch resistance is low is considered to be that there are fine irregularities formed at the time of crystal growth on the film surface, which are caught.
[0006]
In general, as a large area film forming method, a uniform thin film is easily obtained and a sputtering method with less environmental pollution is suitable.
Sputtering methods are roughly classified into a high frequency (RF) sputtering method using a high frequency power source and a direct current (DC) sputtering method using a direct current power source. The RF sputtering method is excellent in that an electrically insulating material can be used as a target. However, a high-frequency power source is expensive and complicated in structure, which is not preferable for film formation over a large area.
[0007]
In the DC sputtering method, the target material is limited to a material having good conductivity. However, the DC sputtering method is preferable as an industrial film forming method because a direct current power source having a simple device structure is used. JP-A-1-97315 proposes a method for forming a tin oxide conductive film by a sputtering method, but only describes an RF sputtering method and has not yet adopted a DC sputtering method. Further, only a relatively high resistance film having a specific resistance of 8 × 10 ⁻³ Ωcm or more can be obtained.
[0008]
JP-A-7-33030 discloses a transparent conductive oxide comprising one or more transparent conductive oxides selected from the group consisting of In ₂ O ₃ , ZnO, SnO ₂ and Ga ₂ O _3. Although proposed, there is no description of complex oxides mainly composed of tin oxide.
[0009]
JP-A-4-272612 proposes ITO doped with gallium, but indium oxide is the main component and tin oxide is not the main component.
[0010]
[Problems to be solved by the invention]
The present invention eliminates the above-mentioned drawbacks of the prior art, a low resistance and high scratch resistance tin oxide-based transparent conductive film, a method for producing the same, and a sputtering target for forming the tin oxide-based transparent conductive film The purpose is to provide.
[0011]
[Means for Solving the Problems ]
[0012 ]
[0013 ]
[0014 ]
[0015]
The present invention, the total amount of gallium, indium, a sputtering target of tin oxide containing tin as each oxide, a _Ga 2 _{O 3} and _In 2 _{O 3} and SnO ₂ gallium oxide in terms _{of Ga} 2 _{O 3} containing 0.1 to 30 mol% with respect to, and containing 0.1 to 30 mol% based on the total amount of the indium oxide and _Ga 2 _{O 3} and _in 2 _{O 3} and SnO ₂ in _in 2 _{O 3} in terms of A sputtering target is provided.
[0016]
When either gallium oxide or indium oxide is less than 0.1 mol%, the specific resistance of the formed film becomes high, and the film becomes crystalline. Moreover, when either becomes larger than 30 mol%, the specific resistance of a film | membrane will become high.
[0017]
Since the resulting film becomes lower resistance, the content of gallium oxide, 1-15 mol% relative to the total amount of _Ga 2 _{O 3} and _In 2 _{O 3} and SnO ₂ in terms _{of Ga} 2 _{O 3,} and content of indium oxide is preferably 1 to 15 mol% relative to the total amount of _Ga 2 _{O 3} and _in 2 _{O 3} and SnO ₂ in _in 2 _{O 3} conversion.
[0018]
Further, since a lower resistance film can be obtained, antimony and / or tellurium, antimony in terms of Sb ₂ O ₅ , tellurium in terms of TeO ₂ , Sb ₂ O ₅ , TeO ₂ , Ga ₂ O ₃ and In it preferably contains 10 mol% or less based on the total amount of the ₂ O ₃ and SnO _2. If it exceeds 10 mol%, the resistance of the target and the resulting film tends to increase. Furthermore, the density (denseness) of the target decreases, and the discharge during sputtering tends to become unstable.
In order to perform stable sputtering discharge, the specific resistance of the sputtering target is preferably 1 Ωcm or less.
[0019]
Gallium oxide in the target, that exist in the oxide state. Here, the oxide state means a state of gallium trioxide (Ga ₂ O ₃ ) or a state of a composite oxide with indium oxide (In ₂ O ₃ ) and / or tin oxide (SnO ₂ ). It is .
[0020]
Indium oxide in the target, that exist in the oxide state. Here, the oxide state is a state of In ₂ O ₃ (SnO ₂ or Ga ₂ O ₃ may be dissolved), or a state of a composite oxide with SnO ₂ and / or Ga ₂ O _3. Means .
[0021]
Gallium oxide and indium oxide are not easy to prepare a transparent film be present in oxide state.
[0022]
When gallium oxide and indium oxide in the sputtering target are present in an oxide state, the maximum particle diameter of the oxide crystal particles is preferably 200 μm or less. The presence of oxide particles having a particle size larger than 200 μm is not preferable because sputtering discharge becomes unstable.
[0023]
The target of the present invention may contain other components as long as the objects and effects of the present invention are not impaired, but it is desirable to keep the amount as small as possible.
[0024]
The composition of the film is basically the same as the composition of the target, but the composition of the film may deviate from the composition of the target depending on the sputtering conditions during film formation.
[0025]
The target of the present invention can be produced by a method for producing ceramics in general, for example, an atmospheric pressure sintering method, a hot press method, etc. However, since a dense target can be produced, it is sintered in an atmosphere containing oxygen such as air. Is preferred.
For example, atmospheric pressure sintering is performed in air at a temperature of 1300 to 1600 ° C. Alternatively, hot pressing is performed in a non-oxidizing atmosphere under conditions of 800 to 1100 ° C.
[0026]
In addition, since the target of the present invention has high conductivity, it is possible to form a film with a large area, and can sufficiently cope with direct current sputtering with a high film forming speed, and also can be applied to any sputtering method such as high frequency sputtering. Yes.
[0027]
The transparent conductive film according to the present invention has a thickness in the range of 3 nm to 5 μm, preferably in the range of 3 to 300 nm.
[0028]
When the film thickness exceeds 5 μm, the film formation time becomes long, resulting in an increase in cost. When the film thickness is thinner than 3 nm, the specific resistance increases.
[0029]
In the transparent heating element according to the present invention, for the purpose of adjusting the appearance, one or more undercoat films are provided between the transparent conductive film layer and the substrate, or one or more overcoats are formed on the transparent conductive film layer. It is possible to adjust the transmission / reflection color tone and the visible light reflectance by using a light interference phenomenon and film absorption by providing a film.
[0030]
The present invention also provides a method for producing a transparent conductive film, wherein the sputtering target is used as a sputtering target in a method for producing a transparent conductive film containing tin oxide as a main component on a substrate by a sputtering method. provide.
[0031]
In the present invention, sputtering is preferably performed in an atmosphere containing an oxidizing gas.
The oxidizing gas means an oxygen atom-containing gas such as O ₂ , H ₂ O, CO, CO ₂ or the like. The concentration of the oxidizing gas greatly affects film characteristics such as film conductivity and light transmittance. Therefore, it is necessary to optimize the concentration of the oxidizing gas under the use conditions such as the apparatus, the substrate temperature, and the back pressure.
[0032]
The sputtering method can be performed by any discharge method such as a DC method and an RF method, but a DC sputtering method with excellent industrial productivity is preferable.
[0033]
Examples of the substrate on which the film is formed include glass, ceramics, plastic, and metal. The temperature of the substrate during the film formation is not particularly limited, but is preferably 300 ° C. or less from the viewpoint of easily obtaining an amorphous film. Further, after the film formation, the substrate can be post-heated (heat treatment).
[0034]
[Action]
In manufacturing the target, gallium oxide and indium oxide serve as an auxiliary for promoting the sintering when the main component tin oxide is sintered. At this time, gallium oxide and indium oxide strengthen each other's action. In addition, gallium oxide and indium oxide also function as an additive that imparts conductivity to the target. Also in this case, gallium oxide and indium oxide strengthen each other's action and lower resistance.
[0035]
Also in the transparent conductive film of the present invention, gallium oxide and indium oxide function as additives for imparting conductivity to the film, as in the target. Also in this case, gallium oxide and indium oxide strengthen each other's action and lower resistance. Further, gallium oxide and indium oxide work to make the film amorphous by the impurity effect.
[0036]
Further, antimony and tellurium work to increase carrier electrons in the film and the target, thereby reducing the resistance of the film and the target.
[0037]
【Example】
(Examples 1-15)
Ga ₂ O ₃ powder, In ₂ O ₃ powder and SnO ₂ powder were prepared, and these powders were mixed at a ratio shown in Table 1 by a dry ball mill.
[0038]
This mixed powder was filled into a rubber mold, pressure-formed with a cold isotropic press device (CIP device), and then fired at a temperature of 1500 ° C. in air. Table 1 shows the density and specific resistance of the sintered body (target). The density was measured by the Archimedes method, and the specific resistance was measured by cutting a 3 × 3 × 30 mm prism sample and measuring by the 4-terminal method.
[0039]
Next, the above-mentioned sintered body was cut into a size of 6 inches in diameter and 5 mm in thickness to produce a target (hereinafter referred to as a GIT target).
Using these various GIT targets, a magnetron DC (direct current) sputtering apparatus is used to form a Ga ₂ O ₃ —In ₂ O ₃ —SnO ₂ -based film (hereinafter referred to as a GIT film). 500 W, introduced gas: Ar—CO ₂ mixed gas, pressure: 4 × 10 ⁻³ Torr, substrate temperature: unheated. Soda lime glass was used for the substrate. The geometric film thickness was about 10 nm.
[0040]
In Examples 1 to 15, the optimum value of the CO ₂ concentration was 10 to 40% by volume (ratio to the sum of argon and CO ₂ of the introduced gas). Table 2 shows the specific resistance and transmittance of the various films obtained.
[0041]
The film composition shown in Table 2 was measured by the ICP method. In this case, the composition of the target and the composition of the film were almost the same.
[0042]
The film was identified by an X-ray diffractometer. In all Examples 1 to 15, the X-ray diffraction pattern was flat and the film was amorphous. FIG. 1 representatively shows the X-ray diffraction pattern of the film obtained in Example 2.
[0043]
(Examples 16 to 19)
A system to which Sb ₂ O ₅ powder or TeO ₂ powder was added was also examined. The mixing ratio of the powder is as shown in Table 1. Targets were prepared as in Examples 1-15. Table 1 shows the density and specific resistance of the sintered body (target).
[0044]
Film formation was performed using a magnetron DC (direct current) sputtering apparatus under the same conditions as in Examples 1 to 15. Table 2 shows the specific resistance and transmittance of the film.
[0045]
The film composition shown in Table 2 was measured by the ICP method. In this case, the composition of the film of Sb ₂ O ₅ and TeO ₂ in the film was considerably smaller than that of the target raw material charged.
[0046]
The film was identified by an X-ray diffractometer. In all Examples 16 to 19, the X-ray diffraction pattern was flat and the film was amorphous.
[0047]
[Table 1]
[0048]
[Table 2]
[0049]
【The invention's effect】
The transparent conductive film of the present invention is rich in chemical resistance, mainly composed of tin oxide, and excellent in chemical resistance such as high acid resistance and alkali resistance.
[0050]
Furthermore, since the film is amorphous, there are no surface irregularities, and since it is smooth, it has excellent scratch resistance, and it is conductive. Has an effect. In particular, since a transparent film can be obtained without heating the substrate, it can be used as an antistatic film having a protective film function such as a plastic film.
[0051]
In addition, the target of the present invention is conductive and can employ a DC sputtering method having a high film formation rate. Further, the target is dense and can be sputtered with a stable discharge.
[Brief description of the drawings]
FIG. 1 shows an X-ray diffraction pattern of a film in Example 2 of the present invention.

Claims (5)

Gallium, indium, a sputtering target of tin oxide containing tin as each oxide, the total amount of _Ga 2 _{O 3} and _In 2 _{O 3} and SnO ₂ gallium oxide in terms _{of Ga} 2 _{O 3} 0 containing .1～30 mol%, and indium oxide and characterized in that it contains 0.1 to 30 mol% relative to the total amount of _Ga 2 _{O 3} and _in 2 _{O 3} and SnO ₂ in _in 2 _{O 3} in terms of Sputtering target. Content of gallium oxide, 1-15 mol% relative to the total amount of _Ga 2 _{O 3} and _In 2 _{O 3} and SnO ₂ in terms _{of Ga} 2 _{O 3,} and the content of indium oxide, _In 2 _{O 3 2.} The sputtering target according to claim 1, which is 1 to 15 mol% in terms of the total amount of Ga ₂ O ₃ , In ₂ O ₃ and SnO _{2 in} terms of conversion. Antimony and / or tellurium, antimony is _Sb 2 _{O 5} in terms, with respect to the total amount of tellurium in TeO ₂ terms, and _Sb 2 _{O 5} and TeO ₂ and _Ga 2 _{O 3} and _In 2 _{O 3} and SnO ₂ 10 The sputtering target according to claim 1 or 2 containing at most mol%. A mixed powder containing Ga ₂ O ₃ powder, In ₂ O ₃ powder and SnO ₂ powder is molded and fired, and gallium oxide is converted into Ga ₂ O _{3 in} terms of Ga ₂ O ₃ , In ₂ O ₃ and SnO ₂ . containing 0.1 to 30 mol% based on the total amount, and the indium oxide 0.1 to 30 mol% content relative to the total amount of _Ga 2 _{O 3} and _in 2 _{O 3} and SnO ₂ in _in 2 _{O 3} conversion A manufacturing method of a sputtering target.   In the method of manufacturing the transparent conductive film which has a tin oxide as a main component on a base | substrate by sputtering method, the transparent conductive film characterized by using the sputtering target of any one of Claims 1-3 as a sputtering target. Manufacturing method.

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